You can try ebay, or google lambo door kit. I remember seeing someone selling the converstion kit on ebay.
I personally would not put lambo doors on my car, I think it's only appropriate on lambos and a few other exotics, hence the name "lambo doors" ...
Also, I thought that picture of the blue E92 with those doors doesnt look that bad.
But in the end, it's your car, do whatever that makes you happy.